code: def _calc_probability(self, count):
      comb_all = self._comb(self.num, self.num_half)
      comb_le_count = 0
      for i in range(count + 1):
          tmp = self._comb(self.num_half, i)
          comb_i = tmp * tmp
          comb_le_count += comb_i
      prob = comb_le_count / comb_all
      return prob
  
imports: import unittest
  import numpy
  import pytest
  import cupy
  from cupy import testing
  from cupy.testing import _condition
label_desc: Use image node_id 3 for calling the TestPermutationRandomness obj's underlying member method code with example usage: obj._calc_probability(count) and returns: prob